Unwanted plants, such as weeds, reduce the amount of resources available to crop plants and can have a negative effect on crop plant yield. Commonly unwanted plants in crop plant environments include broadleaf plants and grasses.
Herbicides are used to kill unwanted plants, such as weeds, in crop plant environments. Herbicides are expensive, and their use may result in unintentional consequences such as groundwater contamination, environmental damage, herbicide-resistant weeds, and human and mammalian health concerns. It is therefore desirable to minimize the amount of herbicides applied to a crop-growing environment or any area in need of weed control.
The herbicide saflufenacil, (N′-[2-chloro-4-fluoro-5-(3-methyl-2,6-dioxo-4-(trifluoromethyl)-3,6-dihydro-1(2H)-pyrimidinyl)benzyl]-N-isopropyl-N-methylsulfamide), is the active ingredient in the commercially available herbicide Sharpen® (available from BASF Chemical Company). Saflufenacil has some activity on horseweed and some activity on grasses at high concentrations, such as concentrations of at least 0.022 lb ai/acre. However, high rates of saflufenacil may damage crop plants. In addition, Sharpen®'s product label cautions that the product should not be applied on soybeans with herbicides such as sulfentrazone or flumioxazin as a tank mix or as a sequential application within 30 days of planting because crop injury may result.
The herbicide flumioxazin, (2-[7-fluoro-3,4-dihydro-3-oxo-4-(2-propynyl)-2H-1,4-benzoxazin-6-yl]-4,5,6,7-tetrahydro-1H-isoindole-1,3(2H)-dione), is the active ingredient in the commercially available herbicide Valor® (available from Valent USA Corporation). Valor® provides excellent broadleaf residual control of weeds such as Palmer amaranth and waterhemp. Valor® is also an excellent pre-emergence herbicide. However, flumioxazin has limited control on large Horseweed (Conyza Canadensis) and on growing grasses. Flumioxazin is not used as a post-emergence herbicide.
Herbicides such as flumioxazin and saflufenacil are protoporphyrinogen oxidase (PPO) inhibitors and use a membrane-disruption mechanism to destroy leaf tissue. PPO is an enzyme that naturally occurs in plants that is crucial to the formation of chlorophyll. When PPO inhibitors prevent PPO activity, singlet oxygen accumulates within plant cells and disrupts cell membranes.
The herbicide 2,4-Dichlorophenoxyacetic acid (“2,4-D”) is a synthetic auxin plant hormone. 2,4-D causes stem curl-over, leaf withering, and eventual plant death by increasing the plants' growth to an unsustainable rate. 2,4-D is used for the control of broadleaf weeds, however, 2,4-D has limited activity on small Horseweed and no activity on grasses.
Unwanted plants, such as weeds, may greatly reduce yields of crop plants. For example, a Horseweed infestation reportedly was responsible for an 80% reduction in soybean yields. Bruce, J. A., and J. J. Kells, Horseweed (Conyza Canadensis) control in no-tillage soybeans (Glycine max) with preplant and preemergence herbicides, Weed Technol. 4:642-647 (1990). Therefore, controlling weeds, and especially grasses and Horseweed, is a major concern of crop growers.
Further, Horseweed and other grasses are becoming resistant to glyphosate. As early as 2000, glyphosate resistant Horseweed was reported in Delaware. Glyphosate resistant Horseweed has since been reported in numerous states. Accordingly, there is a need for new products that can provide effective kill rates of glyphosate resistant Horseweed.
No-till farming has been increasing in popularity because it has many benefits, including decreased labor time and decreased soil erosion. However, one of the downsides of no-till farming is that weeds are harder to control in these areas because they are not subjected to tilling. Accordingly, there is an increasing need for alternative ways to handle weed infestation.
In summary, there is a need for a composition that reduces the amount of herbicides necessary to obtain sufficient weed control while minimizing the harm to crop plants. As more weeds become resistant to herbicides, alternative compositions with high weed control are desired. Further, as no-till farming continues to increase in popularity, there is a greater need for effective herbicides. A composition with effective weed control and lower dosage rate will lead to increased crop plant yields, and decreased environmental, human, and mammalian health concerns.